The construction of passivation layers of this type is known from the document DE 102 34 648. Passivation layers of this type comprise a silicon nitride layer, which covers the topmost interconnect structure of the semiconductor chip, and a polyimide layer arranged on the silicon nitride layer. While the silicon nitride layer ensures that no metallic ions diffuse into the insulation layers composed of silicon dioxide on the top side of a semiconductor chip to the sensitive PN junction zones, the polyimide layer ensures that the transition from the ceramic silicon nitride layer to a plastic housing composition is improved in order to minimize delaminations between the top side of the semiconductor chip and the plastic housing composition.
The passivation layer composed of silicon nitride has hitherto been applied to the aluminum metallization layer of the interconnect structure in front-end fashion with the disadvantage of a relatively high hardness and brittleness of the silicon nitride layer, which, in the case of increased mechanical stress, can lead to fractures in said passivation layer composed of silicon nitride and thus causes corrosion of the aluminum metallization lying at a deeper level. Onto this ceramic insulation layer, as described above, a polyimide layer is applied to the chip surface in order to improve the adhesiveness of a plastic housing composition with the chip top side. However, said passivation layer has the disadvantage that a thermal insulation of the semiconductor chip surface is also associated therewith, especially as the thermal conductivity of the polyimide is approximately a factor of 100 poorer than the thermal conductivity of the silicon nitride. Moreover, the application of a ceramic layer composed of silicon nitride and the subsequent application of a polyimide layer are not unproblematic. The methods used for this purpose are cost-intensive especially as the polyimide layer and the silicon nitride layer are applied in two different processes in the front end, which does not reduce the costs in terms of production technology.